Water usage

While water is a critical resource for Eskom, it is also a scarce resource in South Africa. Eskom consumes about 2% of the country’s freshwater resources and this calls for continual improvement in performance.

Eskom largely uses freshwater resources from government water schemes. In the period under review, approximately 8 000ML of mine water was used at Tutuka and Lethabo power stations. We are implementing a mine water recovery project to use approximately 6ML/day of mine water at Duvha power station.

The increase in water usage was partially influenced by the quality of raw water received, the deteriorating thermal efficiency at some power stations and the considerable load generated at power stations that are not as water efficient as the modern wetcooled power stations.

Although the 2008 performance did not meet target, it has improved compared with the 2007 performance, even though production from wet-cooled stations exceeded planned levels. Water management studies have been commissioned with the aim of identifying improvement opportunities.

Increased demand for electricity is expected to result in higher water consumption over the next five years. Although the next generation of coal-fired power stations will be supercritical drycooled power stations, overall water consumption is expected to increase by about 14 million cubic metres per annum. This includes the use of water in the flue gas desulphurisation process.

Eskom continues to work with the Department of Water Affairs and Forestry (DWAF) to ensure the effective and efficient management of raw water supply infrastructure. This includes transfer schemes serving existing power stations, planning raw water supply infrastructure projects for new power stations and the timely and efficient processing and authorisation of water-use licence applications. We have secured our water supplies through long-term water supply and payment contracts with DWAF.

DWAF, through its project funding and implementation arm, Trans Caledon Tunnel Authority, is implementing the Vaal River Eastern Sub-system Augmentation Project. This was approved by the South African government to augment raw water from the Vaal Dam to supply Eskom and Sasol’s growing water demands in Mpumalanga. The project is due to deliver water by September 2008.

Plans are also well advanced to augment water supplies by transferring surplus effluent return flows from the Crocodile River (West)/Marico water management area, to the Mokolo catchment in the Limpopo water management area. This will enhance water supply to the Matimba and Medupi power stations in the Lephalale area.

Eskom has been actively involved in the support and development of catchment management agencies (CMAs) and has to date participated in the development of the Inkomati, Usuthu to Mhlatuze and Limpopo CMAs.

Water is a critical resource in Eskom, but is also a scarce resource in South Africa. Eskom consumes approximately 2% of the country’s freshwater resources, therefore the need for continual improvement in performance. In addition, climate change is expected to impact the distribution and availability of freshwater resources in the country.

• the focus of water demand management on the recovery of mine water to power stations
• the development of best-practice guidelines to assist in continual improvement in practices
• engaging power stations on a quarterly basis to analyse their water use performance and developing plans to improve poor performance
• conducting training of power station staff on water use efficiency improvements and water management
• sharing and incorporation of recommendations from the water conservation/water demand management study done by DWAF

The Minister of Water Affairs and Forestry, Lindiwe Hendricks, and the Chief Executive of Eskom, Jacob Maroga signed a memorandum of understanding (MoU) on 19 March 2008 to facilitate broader cooperation on efficient water usage at Eskom’s power stations as well as to establish a strategic partnership to encourage the sustainable use and availability of water and energy resources into the future.

The signing of the MoU between DWAF and Eskom marks the beginning of a new phase that creates a culture of collaboration in many areas, including the fundamental challenges facing both the water and energy sectors to improve efficiencies.

At the inaugural Water Conservation and Water Demand Management (WC/WDM) Sector Awards, Eskom (Duvha power station) was honoured by the Minister of Water Affairs and Forestry for our contribution to the WC/WDM programme.

The water sector is undergoing an institutional reform process with the establishment of various institutions such as catchment management agencies, water user associations and the South African National Water Resources Infrastructure Agency (SANWRIA). We have been actively involved in the development process of these new institutions that relate to our business interests. We foresee the impending establishment of the SANWRIA to be a significant development in the water sector, as this organisation will be our primary supplier of raw water.

Since the 1970s the limitations of the water resources of South Africa have motivated Eskom’s engineers to find ways to conserve water. The most effective of the solutions is dry cooling. This technology has since been introduced, resulting in two of the biggest dry-cooled power stations in the world. This has led to the saving of over 200 million litres of water per day that would normally have been lost through evaporation.

Matimba power station near Lephalale in the Limpopo province is the largest direct-dry-cooled station in the world, producing more than 4 000MW. It makes use of closed-circuit cooling technology similar to the radiator and fan system used in cars. Water consumption is about 0,1 litres per kWh of electricity sent out, compared with about 1,9 litres on average for the wet-cooled stations.

The choice of dry-cooled technology for Matimba was largely influenced by the scarcity of water in the area. Kendal power station near Witbank in the Mpumalanga province is the largest indirect dry-cooled power station in the world, with water consumption of about 0,08 litres per kWh of electricity sent out. Indirect dry-cooling entails the cooling of the water through indirect contact with air in a cooling tower, a process during which virtually no water is lost in the transfer of the waste heat.

At Eskom’s wet-cooled stations, improved water management has resulted in extensive reuse of water. The so-called zero liquid effluent discharge (ZLED) policy means in essence that water is cascaded from good to poor-quality uses until all pollutants are finally captured in the ash dams. The aim is to get rid of most of the salts with the smallest possible volume of water without compromising the ability of the ash system to encapsulate these salts. Open re-circulating cooling water systems are operated at high cycles of concentration to ensure that water use is minimised (typically 15-20 cycles of concentration, on average).

The amount of energy produced by Eskom's coal-fired power stations over the period 1993 to 2004 has increased by 43%, while the corresponding increase in water consumption was only 27%. The commissioning of Kendal, Matimba and other dry-cooled units since the late 1980s is the main reason for the organisation’s improved water efficiency. The cumulative saving is about 1 400 million m3 over the period if compared to the quantity of water that would have been used if these power stations had been wet-cooled.

Access to water and water availability remain key factors in ensuring the sustainability of development in Southern Africa. Eskom’s efforts to use this precious resource more efficiently are an integral part of the company’s commitment to sustainable development.

• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 8
• 9
• 10